R.-Boyle's New the plane of flotation, the stability of the instrument when floating will be diminished or destroyed.
In the centesimal hydrometer of Francceur the volume of the stem between successive divisions of the scale is always, oath of the whole volume immersed when the instrument floats in water at 4° C. In order to graduate the stem the instrument is first weighed, then immersed in distilled water at 4° C., and the line of flotation 7.1 F marked zero.
Then the reading of the scale at the line of flotation, added to the number on the weight, gives the reading required.
Common's telescope presents many ingenious features, especially the relief-friction by flotation of the polar axis in mercury, and in the arrangements of the observatory for giving ready access to the eye-piece of the telescope.
The only facts in natural history which appear even indirectly to countenance the flotation theory are the presence of a swimming bladder in some fishes, and the existence of membranous expansions or pseudowings in certain animals, such as the flying fish, flying dragon and flying squirrel.